At the early development of the embryo, short bristles were observed on each side of upper jaw in Neophocaena phocaenoides. The number of the bristles varied from 1-3 on the left and 2-3 on the right. Semicircle ear outline was visible. The penis of male foetus was exposed out of body. The swimming organs (flipper, fluke and midway anus to fluke notch) developed prominently. As embryo developed, external ear outline of foetus disappeared and the penis of male foetus concealed in the penial pouch. These morphological changes in the course of the embryo development indicated that cetacean ancestor might have lived on land and that cetacean adapted to water environment when coming into water secondly. In addition, statistical analysis on 17 foetuses and juveniles showed that: the growth rate of foetus was 9.08 cm/month (0.303 cm/day) in Neophocaena phocaenoides, the gestation period may be about 9.4 months in Neophocaena phocaenoides in the Yangtze River, and mating may take place from June to August, parturition time from March to May each year.